Method and apparatus for thermoelectric cooling of fluids

ABSTRACT

The present disclosure provides a method and a thermoelectric cooling apparatus for cooling a fluid. The thermoelectric cooling apparatus comprises one or more of thermoelectric devices, a hot sink, a cold sink, and a heat rejection apparatus which comprises condenser fins and a fan to attain a high figure of merit. The heat from the fluid is transferred to the hot sink and/or one or more heat pipes by the one or more thermoelectric devices. The heat from the one or more heat pipes is dissipated to the ambient through condenser fins and the fan.

BACKGROUND

The present disclosure relates to thermoelectric cooling of fluids. Morespecifically, it relates to an efficient method and a device forthermoelectric cooling of fluids.

The most widely used type of cooling system is a vapor compressionsystem, which uses chlorofluorocarbon (CFC)-based refrigerants to coolfluids. It has a high co-efficient of performance (COP). However, theuse of CFC-based refrigerants in the vapor compression system forcooling poses an environmental threat because CFCs may lead to adepletion of the ozone layer.

An alternative to the vapor compression system for cooling fluids is athermoelectric cooling system which is environment friendly, effective,and simple in construction. However, there exists a limitation in thethermoelectric cooling system—its COP is about one third the COP of avapor compression system. To increase the COP of the thermoelectriccooling system, much effort has been made in the past to optimize itsheat dissipation methods and device level designs, among other things.

Other limitations of conventional thermoelectric cooling systems includepoor power utilization techniques. Continuously switching ON thethermoelectric cooling system results in increased power consumption,thereby increasing the cost of cooling per liter of fluid.

While thermoelectric cooling systems and methods for their operationhave been developed in the past, there exists a need for furtherdevelopment in designing thermoelectric cooling systems to increase theCOP.

SUMMARY

An objective of the present disclosure is to provide a thermoelectriccooling apparatus with an improved design and a high co-efficient ofperformance. Though the thermoelectric cooling apparatus according tothe present disclosure is used to cool fluids, other forms of materialssuch as semi-liquids, semi-solids, colloids, and gels phased substances,can also be cooled using the thermoelectric cooling apparatus disclosed.

In an embodiment of the present disclosure, a thermoelectric coolingapparatus comprises one or more thermoelectric devices, one or moremetal standoffs, a cold sink, one or more heat pipes and condenser fins.The one or more thermoelectric devices are configured to cool a fluid,the one or more thermoelectric devices comprising a hot side and a coldside. The one or more metal standoffs comprise a first side and a secondside. The first side of the one or more metal standoffs is attached tothe cold side of the one or more thermoelectric devices, wherein the oneor more metal standoffs are configured to transfer heat to the cold sideof the one or more thermoelectric devices. The cold sink is attached tothe second side of the one or more metal standoffs, the cold sink beingconfigured to transfer heat from the fluid to the one or more metalstandoffs. The one or more heat pipes comprise a first end and a secondend. The first end is attached to the hot side of the one or morethermoelectric devices, wherein the one or more heat pipes areconfigured to assist in transfer of heat from the hot side of the one ormore thermoelectric devices to the ambient. The condenser fins areattached to the second end of the one or more heat pipes. The condenserfins are configured to assist in dissipating heat from the second end ofthe one or more heat pipes to the ambient.

The thermoelectric cooling apparatus according the present embodimentfurther comprises a hot sink attached to the first end of the one ormore heat pipes, wherein the hot sink is configured to assist indissipating heat from the first end of the one or more heat pipes.

The thermoelectric cooling apparatus according the present embodimentmay further comprise a plurality of screws, wherein the plurality ofscrews is configured to facilitate attachment of the hot sink and thecold sink.

The thermoelectric cooling apparatus according the present embodimentmay further comprise a plurality of grommets, wherein the plurality ofgrommets is configured to prevent heat conduction from the hot sink tothe cold sink.

The thermoelectric cooling apparatus according the present embodimentmay further comprise a hot sink fan thermally coupled to the hot sink,wherein the fan is configured to dissipate heat from the hot sink to theambient.

The thermoelectric cooling apparatus according the present embodimentmay further comprise a fan thermally coupled to the condenser fins,wherein the fan is configured to dissipate heat from the condenser finsto the ambient.

The thermoelectric cooling apparatus according the present embodimentmay further comprise an evaporator plate thermally coupled to the hotside of the one or more thermoelectric devices, wherein the evaporatorplate is configured to collect heat from the hot side of the one or morethermoelectric devices.

In the thermoelectric cooling apparatus of above explained embodiment,the cold sink comprises at least one of anodized aluminum, copper andnickel.

The thermoelectric cooling apparatus according to the present embodimentmay further comprise an insulation material, wherein the insulationmaterial is configured to fill gaps between elements of thethermoelectric cooling apparatus.

The thermoelectric cooling apparatus according to the present embodimentmay further comprise a thermal diode positioned between the hot side ofthe one or more thermoelectric devices and the one or more heat pipes,wherein the thermal diode is configured for unidirectional heattransfer.

The thermoelectric cooling apparatus according to the present embodimentmay further comprise one or more containers containing the fluid,wherein one of the one or more containers is configured to function as athermal capacitor.

A thermoelectric cooling apparatus in accordance with another embodimentcomprises one or more thermoelectric devices, a cold sink, one or morediodic heat pipes, and a fin array. The one or more thermoelectricdevices comprise a hot side and a cold side, wherein the one or morethermoelectric devices are configured to cool a fluid. The cold sink isattached to the cold side of the one or more thermoelectric devices, thecold sink being configured to transfer heat from the fluid to the one ormore thermoelectric devices. The one or more diodic heat pipes comprisea first end and a second end The first end of one or more diodic heatpipes is attached to the hot side of the one or more thermoelectricdevices, wherein the one or more diodic heat pipes are configured tofacilitate transfer heat from the hot side of the one or morethermoelectric devices to the ambient. The fin array is attached to thesecond end of the one or more heat pipes, wherein the fin array isconfigured to transfer heat from the second end of the one or more heatpipes.

The thermoelectric cooling apparatus in accordance with the presentembodiment may further comprise condenser fins attached to the one ormore heat pipes, wherein the condenser fins are configured to assist indissipation of heat from the one or more heat pipes.

The thermoelectric cooling apparatus in accordance with the presentembodiment may further comprise a fan thermally coupled to the condenserfins, wherein the fan is configured to dissipate heat from the condenserfins to the ambient.

A thermoelectric cooling apparatus in accordance with yet anotherembodiment comprises one or more thermoelectric devices, one or moremetal standoffs, one or more cold sinks, and one or more heat pipes. Theone or more thermoelectric devices comprise a hot side and a cold side,wherein the one or more thermoelectric devices are configured to cool afluid. The one or more metal standoffs comprise a first side and asecond side. The first side of the one or more metal standoffs isattached to the cold side of the one or more thermoelectric devices,wherein the one or more metal standoffs are configured to transfer heatto the cold side of the one or more thermoelectric devices. The one ormore cold sinks are attached to the second side of the one or more metalstandoffs, the cold sink being configured to transfer heat from thefluid to the one or more metal standoffs. The one or more heat pipescomprise a first end and a second end. The first end of the one or moreheat pipes is attached to the hot side of the one or more thermoelectricdevices, wherein the one or more heat pipes are configured to assist indissipating heat from the hot side of the one or more thermoelectricdevices to the ambient.

The thermoelectric cooling apparatus in accordance with the presentembodiment may further comprise condenser fins and a fan, the condenserfins being attached to the second end of the one or more heat pipes,wherein the condenser fins and the fan are configured to dissipate heatfrom the one or more heat pipes to the ambient.

The thermoelectric cooling apparatus in accordance with the presentembodiment may further comprise an insulated section to prevent theconduction of heat from the second end to the first end of the one ormore heat pipes.

The thermoelectric cooling apparatus in accordance with the presentembodiment may further comprise an evaporator plate thermally coupled tothe hot side of the one or more thermoelectric devices, wherein theevaporator plate is configured to collect heat from the hot side of theone or more thermoelectric devices.

A thermoelectric cooling apparatus in accordance with yet anotherembodiment comprises one or more thermoelectric devices, one or moremetal standoffs, a cold sink, and a separator. The one or morethermoelectric devices comprise a hot side and a cold side, wherein theone or more thermoelectric devices are configured to cool a fluid. Theone or more metal standoffs comprise a first side and a second side. Thefirst side of the one or more metal standoffs is attached to the coldside of the one or more thermoelectric devices, wherein the one or moremetal standoffs are configured to transfer heat to the cold side of theone or more thermoelectric devices. The cold sink is attached to thesecond side of the one or more metal standoffs, the cold sink beingconfigured to transfer heat from the fluid to the one or more metalstandoffs. The separator is configured to direct the fluid towards thecold sink. The separator may comprise a plurality of pores.

The thermoelectric cooling apparatus in accordance with the presentembodiment may further comprise a convective heat dissipation apparatusthermally coupled to the hot side of the one or more thermoelectricdevices. The convective heat dissipation apparatus is configured toremove heat from the hot side of the one or more thermoelectric devicesto the ambient, wherein the convective heat dissipation apparatuscomprises a convective fluid for heat transportation, a heat spreader, apump, fins and a fan.

A thermoelectric cooling apparatus with yet another embodiment comprisesone or more thermoelectric devices, one or more metal standoffs, a coldsink and a heat pipe-heat sink assembly. The one or more thermoelectricdevices comprise a hot side and a cold side, wherein the one or morethermoelectric devices are configured to cool a fluid. The one or moremetal standoffs comprise a first side and a second side. The first sideof the one or more metal standoffs is attached to the cold side of theone or more thermoelectric devices, wherein the one or more metalstandoffs are configured to transfer heat to the cold side of the one ormore thermoelectric devices. The cold sink is attached to the secondside of the one or more metal standoffs, the cold sink being configuredto transfer heat from the fluid to the one or more metal standoffs. Theheat pipe-heat sink assembly is attached to the hot side of the one ormore thermoelectric devices, wherein the heat pipe-heat sink assembly isconfigured to dissipate heat from the hot side of the one or morethermoelectric devices to the ambient.

The thermoelectric cooling apparatus in accordance with the presentembodiment may further comprise a fan thermally coupled to the heatpipe-heat sink assembly, wherein the fan is configured to dissipate heatfrom the heat pipe-heat sink assembly to the ambient.

A method of cooling a fluid by using a thermoelectric apparatuscomprises operating the thermoelectric apparatus at optimum conditionswhen the temperature of the fluid is not within a predeterminedtemperature range, determining the temperature of the fluid atpredetermined time intervals, and operating the thermoelectric apparatusat steady state conditions when the temperature of the fluid is withinthe predetermined temperature range.

Further, in the method according to the present embodiment, operatingthe thermoelectric apparatus at optimum conditions includes supplying anoptimum current (I_(opt)) to the thermoelectric apparatus.

Furthermore, in the method according to the present embodiment,operating the thermoelectric apparatus at steady state conditionsincludes supplying a steady state current (I_(ss)) to the thermoelectricapparatus.

In an embodiment of the present disclosure, a method of operating athermoelectric cooling apparatus for cooling a fluid is disclosed.According to the embodiment, the method comprises selecting at least onemode of operation from a plurality of modes of operation for thethermoelectric cooling apparatus, and supplying a maximum voltage(V_(max)) or minimum voltage (V_(min)) to the thermoelectric coolingapparatus based on the selected mode of operation.

The plurality of modes according to the present method, includes a highpower mode and a power efficiency mode.

Further, the method in accordance with the present embodiment furthercomprises switching from V_(min) to V_(max) when the temperature of thefluid is greater than a predetermined temperature (T_(w)).

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments of the disclosure will hereinafter bedescribed in conjunction with the appended drawings provided toillustrate and not to limit the disclosure, wherein like designationsdenote like elements, and in which

FIG. 1 illustrates a side view of a thermoelectric cooling unit, inaccordance with an embodiment of the present disclosure;

FIG. 2 illustrates a perspective view of a thermoelectric cooling unit,in accordance with an embodiment of the present disclosure;

FIG. 3 illustrates a perspective view of a thermoelectric coolingapparatus, in accordance with an embodiment of the present disclosure;

FIG. 4 illustrates a cross-sectional view of a thermoelectric coolingapparatus, in accordance with an embodiment of the present disclosure;

FIG. 5 illustrates a cross-sectional view of a thermoelectric coolingunit, in accordance with another embodiment of the present disclosure;

FIG. 6 illustrates a cross-sectional view of a thermoelectric coolingapparatus, in accordance with another embodiment of the presentdisclosure;

FIG. 7 illustrates a cross-sectional view of a thermoelectric coolingapparatus, in accordance with yet another embodiment of the presentdisclosure;

FIG. 8 illustrates a cross-sectional view of a thermoelectric coolingapparatus, in accordance with yet another embodiment of the presentdisclosure;

FIG. 9 illustrates a cross-sectional view of a thermoelectric coolingapparatus, in accordance with yet another embodiment of the presentdisclosure;

FIG. 10 illustrates a cross-sectional view of a thermoelectric coolingapparatus, in accordance with yet another embodiment of the presentdisclosure;

FIG. 11 illustrates a cross-sectional view of a thermoelectric coolingapparatus, in accordance with yet another embodiment of the presentdisclosure;

FIG. 12 illustrates a cross-sectional view of a thermoelectric coolingapparatus, in accordance with yet another embodiment of the presentdisclosure;

FIG. 13 illustrates a cross-sectional view of a thermoelectric coolingapparatus, in accordance with yet another embodiment of the presentdisclosure;

FIG. 14 illustrates a cross-sectional view of a thermoelectric coolingapparatus, in accordance with yet another embodiment of the presentdisclosure;

FIG. 15 illustrates a cross-sectional view of a thermoelectric coolingapparatus, in accordance with yet another embodiment of the presentdisclosure;

FIG. 16 illustrates graphs depicting variations in temperature andcurrent with time for a thermoelectric cooling apparatus, in accordancewith an embodiment of the present disclosure;

FIG. 17 illustrates graphs depicting variations in temperature andcurrent with time for a thermoelectric cooling apparatus, in accordancewith another embodiment of the present disclosure;

FIG. 18 illustrates graphs depicting variations in temperature andcurrent with time for a thermoelectric cooling apparatus, in accordancewith yet another embodiment of the present disclosure; and

FIG. 19 illustrates a flow chart representing a method of operation of athermoelectric cooling apparatus.

DESCRIPTION OF EMBODIMENTS

Before describing the embodiments in detail, in accordance with thepresent disclosure, it should be observed that these embodiments resideprimarily in the method and apparatus for cooling of fluids.Accordingly, steps of the method and the apparatus components have beenrepresented to show only those specific details that are pertinent foran understanding of the embodiments of the present disclosure, and notthe details that will be apparent to those with ordinary skill in theart.

FIG. 1 illustrates a side view of a thermoelectric cooling unit 100, inaccordance with an embodiment of the present disclosure.

The thermoelectric cooling unit 100 comprises thermoelectric devices102, metal standoffs 104, a cold sink 106, a hot sink 108, heat pipes110, condenser fins 114, and a fan 116.

The thermoelectric devices 102 comprise a hot side and a cold side (notshown in the figure). In an embodiment of the present disclosure,thermoelectric devices 102 comprises thermoelectric modules of differentQ_(max) (Q_(max) is defined as the maximum cooling capacity of thethermoelectric module for ΔT=0). The cold side of thermoelectric devices102 is thermally connected to cold sink 106 through metal standoffs 104.Metal standoffs 104 are configured to transfer heat from cold sink 106to thermoelectric devices 102. Metal standoffs 104 further preventthermal losses by increasing the separation between the hot side ofthermoelectric devices 102 and cold sink 106. Cold sink 106 is incontact with a fluid (not shown in the figure). The hot side ofthermoelectric devices 102 is attached to hot sink 108. In an embodimentof the present disclosure, hot sink 108 is made of extruded anodizedaluminum. In another embodiment of the present disclosure, hot sink 108comprises metals such as nickel, which prevent surface oxidation andfacilitates soldering. Hot sink 108 and cold sink 106 comprise aplurality of fins that are optimized for natural convection in thefluid. Hot sink 108 and cold sink 106 are physically connected usingscrews 118. Grommets 112 prevent conduction from hot sink 108 to coldsink 106 through screws 118.

Further, heat pipes 110 are positioned between the hot side ofthermoelectric devices 102 and hot sink 108. Heat pipes 110 comprise afirst end and a second end (not shown in figure). The first end of heatpipes 110 is attached to the hot side of thermoelectric devices 102. Inan embodiment of the present disclosure, each of thermoelectric devices102 is connected to each of heat pipes 110. The second end of heat pipes110 is connected to condenser fins 114. In an embodiment of the presentdisclosure, heat pipes 110 are unidirectional, i.e. they conduct heat inonly one direction, from the first end to the second end. In anotherembodiment of the present disclosure, heat pipes 110 are bidirectional,i.e. they conduct heat in both directions based on the temperaturegradient.

When thermoelectric devices 102 are switched ON, heat is extracted fromthe fluid through cold sink 106 and metal standoffs 104, thus coolingthe fluid. Thermoelectric devices 102 transfer heat from cold sink 106and metal standoffs 104 to the hot side of thermoelectric devices 102.The heat is dissipated from the hot side through a heat transferassembly and hot sink 108. The heat transfer assembly comprises heatpipes 110, condenser fins 114 and fan 116. In an embodiment of thepresent disclosure, hot sink 108 is in contact with the fluid to becooled. A part of the heat is transferred to the fluid to be cooled sothat the fluid to be cooled acts as a thermal capacitor.

FIG. 2 illustrates a perspective view of a thermoelectric cooling unit200, in accordance with an embodiment of the present disclosure.

Apart from the elements mentioned in conjunction with FIG. 1,thermoelectric cooling unit 200 comprises a shell 202, an insulationmaterial 204 and grooves 210.

Shell 202 encloses thermoelectric devices 102 (described in conjunctionwith FIG. 1), the first end of heat pipes 110, and metal standoffs 104(described in conjunction with FIG. 1) with the aid of insulationmaterial 204. Insulation material 204 is configured to fill gaps betweenelements of thermoelectric cooling unit. In an embodiment of the presentdisclosure, insulation material 204 is spray type foam. Insulationmaterial 204 fills gaps between elements of thermoelectric cooling unit200 such as thermoelectric devices 102 and metal standoffs 104, inaccordance with the present embodiment. The thermoelectric cooling unit200 further comprises a first hole 206 and a second hole 208 formed inthe insulation. First hole 206 allows a warm fluid (described inconjunction with FIG. 3) to flow from a top container to a bottomcontainer (described in conjunction with FIG. 3). Second hole 208 isconfigured to prevent an air lock that can be caused due to the transferof the warm fluid from the top container to the bottom container.

Further, grooves 210 are present at a top side and a bottom side ofthermoelectric cooling unit 200. In the insulation, grooves 210 areconfigured to position O-rings and to fit the top container and thebottom container. In an embodiment of the present disclosure, O-ringsare rubber gaskets. Usage of the rubber gaskets makes the assembly fluidtight. Fins 212 of hot sink 108 are in thermal contact with the warmfluid present in the input container. Similarly, fins 214 of cold sink106 are in thermal contact with the cold fluid present in the outputchamber. In an embodiment of the present disclosure, fins 212 and 214are made of aluminum.

The warm fluid present at the input container flows to the outputcontainer through first hole 206. Cold sink 106 is in thermal contactwith the cold fluid. When thermoelectric devices 102 are switched ON,heat from the cold fluid is transferred to the hot side ofthermoelectric devices 102 through cold sink 106. A first portion of theheat dissipated at the hot side of thermoelectric devices 102 istransferred to hot sink 108 and the warm fluid. A second portion of theheat dissipated at the hot side of thermoelectric devices 102 istransferred to the ambient through heat pipes 110 and condenser fins114.

FIG. 3 illustrates a perspective view of a thermoelectric coolingapparatus 300, in accordance with an embodiment of the presentdisclosure.

Thermoelectric cooling apparatus 300 comprises a thermoelectric coolingunit 200, a top container 302, a bottom container 304, a fluid storagechamber 306, a fluid dispenser 312, and an insulated pipe 314.

Fluid storage chamber 306 stores a warm fluid 308 that needs to becooled. Warm fluid 308 is also present in top container 302. Warm fluid308 present in top container 302 is in thermal contact with hot sink 108of thermoelectric cooling unit 200. In an embodiment of the presentdisclosure, top container 302 that comprises the warm fluid 308 acts asa thermal capacitor. The outer body of top container 302 is made ofmaterials such as plastic or thin metal sheet, which may aid indischarging the thermal capacitor. Warm fluid 308 is transferred fromfluid storage chamber 306 to bottom container 304 through insulated pipe314 that connects fluid storage chamber 306 and bottom container 304.Bottom container 304 comprises cold fluid 310. In an embodiment of thepresent disclosure, bottom container 304 is insulated to prevent heatleakage from the ambient to cold fluid 310. The walls of the bottomcontainer 304 are made of either plastic material or thin metal sheet.Cold fluid 310 is dispensed out of bottom container 304 through fluiddispenser 312.

When thermoelectric cooling unit 200 is switched ON, heat from coldfluid 310 is transferred to warm fluid 308 present in top container 302.Cold fluid 310 is dispensed from the bottom container 304 through fluiddispenser 312. As the level of cold fluid 310 decreases in bottomcontainer 304, warm fluid 308 is dispensed from fluid storage chamber306 to bottom container 304 through insulated pipe 314. Insulated pipe314 prevents transfer of heat from warm fluid 308 present in topcontainer 302 to warm fluid 308 which is transferred from fluid storagechamber 306 to bottom container 304.

FIG. 4 illustrates a cross-sectional view of a thermoelectric coolingapparatus 400, in accordance with another embodiment of the presentdisclosure.

Apart from the elements mentioned in conjunction with FIG. 1, FIG. 2,and FIG. 3, thermoelectric cooling apparatus 400 comprises a separator402.

Separator plate 402 is present in bottom container 304 and positionedbelow first hole 206. In an embodiment of the present disclosure,separator 402 is made of plastic. Separator 402 directs the flow of warmfluid 308 toward cold sink 108 and ensures that warm fluid 308 from topcontainer 302 does not directly reach the bottom portion of bottomcontainer 304 and that warm fluid 308 contacts cold sink 106. Warm fluid308 is cooled when it comes in contact with cold sink 106. Cold fluid310 is heavier and denser than warm fluid 308, and thus reaches thebottom portion of bottom container 304. Cold fluid 310 is then dispensedthrough fluid dispenser 312.

FIG. 5 illustrates a cross-sectional view of a thermoelectric coolingunit 500, in accordance with another embodiment of the presentdisclosure.

Thermoelectric cooling unit 500 comprises thermoelectric devices 102,metal standoffs 104, cold sink 106, hot sink 108, heat pipes 502,condenser fins 114, fan 116, and a hot sink fan 504.

In thermoelectric cooling unit 500, thermoelectric devices 102, heatpipes 502, cold sink 106 and hot sink 108 are in a vertical orientation.Cold sink 106 is in thermal contact with the cold fluid. The cold sideof thermoelectric devices 102 is attached to metal standoffs 104. Thehot side of thermoelectric devices 102 is attached to heat pipes 502 andhot sink 108. Hot sink fan 504 is attached in close proximity to hotsink 108 to dissipate heat to the ambient.

When thermoelectric devices 102 are switched ON, cold sink 106 collectsheat from the cold fluid (not shown in the figure). The heat rejected bythe thermoelectric devices 102 is transferred to the ambient by twopaths. One heat rejection path comprises hot sink 108 in combinationwith hot sink fan 504. The other heat rejection path comprises heatpipes 502. A working fluid present in heat pipes 502 transfers heat tocondenser fins 114. Fan 116 facilitates dissipation of heat fromcondenser fins 114 to the ambient.

The total heat rejected to the ambient (Q_(total)) is a sum of twoparameters, electrical energy consumed by thermoelectric devices 502(Q_(electrical)) and the heat extracted from the cold fluid(Q_(cooling)), given by:

Q _(total) =Q _(electrical) +Q _(cooling)  (1)

The conductance (K_(total)) of thermoelectric cooling unit 500 is a sumof two factors, conductance of heat pipes 510 (K_(HP)) and conductanceof hot sink 504 (K_(hotsink)). In other terms,

K _(total) =K _(HP) +K _(hotsink)  (2)

Also,

T(TEC _(hot side))−T(Ambient)=ΔT _(HS) =Q _(total) /K _(total)  (3)

Where,

T(TEC_(hot side)) is the temperature of the hot side of thermoelectricdevices 502;

T(Ambient) is the ambient temperature; and

ΔT_(HS) is the temperature differential across thermoelectric devices502.

Hence, K_(total) is always greater than K_(HP). Further, ΔT_(HS) (withhot sink 108) is less than ΔT_(HS) (without hot sink 108). Astemperature differential across thermoelectric devices 502 is reduced,efficiency of thermoelectric cooling unit 500 increases.

FIG. 6 illustrates a cross-sectional view of a thermoelectric coolingapparatus 600, in accordance with another embodiment of the presentdisclosure.

Thermoelectric cooling apparatus 600 comprises a first container 602, asecond container 604, cold sink 106, metal standoffs 104, thermoelectricdevices 102, hot sink 108, heat pipes 606, condenser fins 114, and fan116.

First container 602 contains cold fluid 310. Cold sink 106 is in contactwith cold fluid 310. Metal standoffs 104 are present between cold sink106 and the cold side of thermoelectric devices 102. The hot side ofthermoelectric devices 102 is attached to hot sink 108 and the first endof heat pipes 606. Hot sink 108 is in contact with warm fluid 308, whichis present in second container 604. The second end of heat pipes 606 isconnected to condenser fins 114. Fan 116 is connected to condenser fins114.

When thermoelectric devices 102 are switched ON, heat from cold fluid310 is transferred through cold sink 106 and metal standoffs 104 to thehot side of thermoelectric devices 102. Heat from the hot side ofthermoelectric devices 102 is conducted through two components—hot sink108 and heat pipes 606. Hot sink 108 transfers the heat to secondcontainer 604 that contains warm fluid 308. In an embodiment of thepresent disclosure, an assembly of second container 604 and warm fluid308 act as a thermal capacitor. In another embodiment of the presentdisclosure, warm fluid 308 contains encapsulated phase change materialswhich maintain a constant temperature of the fluid 308. Further, heatfrom heat pipes 606 is transferred to condenser fins 114 by a workingfluid (not shown in the figure) present in heat pipes 606. Fan 116facilitates the dissipation of the heat from condenser fins 114 to theambient.

During operation of thermoelectric cooling apparatus 600, heattransferred while cooling cold fluid 310 is given by Q_(cooling), whichis equal to the amount of heat transferred during an initial transientstage process, Q_(transient-cooling).

A total amount of heat (Q_(total)) transferred by thermoelectric coolingapparatus 600 is given by,

Q _(total) =Q _(electrical) +Q _(cooling)  (4)

Where,

Q_(electrical) is the electrical energy consumed by thermoelectricdevices 102.

The total amount of heat extracted from first container 602 is given by,

Q _(total) =Q _(HP) +Q _(capacitor)  (5)

Where,

Q_(HP) is the amount of heat transferred to heat pipes 606 and

Q_(capacitor) is the amount of heat transferred to second container 604.

Further,

Q _(capacitor) =mC _(capacitor) ΔT _(capacitor)  (6)

Where,

m=mass of second container 604 with warm fluid 308;

C_(capacitor) is specific heat of the assembly of second container 604and warm fluid 308; and

ΔT_(capacitor) is temperature increase in the assembly of secondcontainer 604 and warm fluid 308.

During a transient stage of removal of heat from cold fluid 310,ΔT_(capacitor) increases proportionally with time, in an embodiment ofthe present invention. After the transient stage of transferring heatfrom cold fluid 310 (Q_(transient-cooling)), the amount of heat removedfrom cold fluid 310 attains a steady state amount of heat(Q_(steady state)), which is desirable to maintain cold fluid 310 in adesired temperature range. Since Q_(steady state) is less thanQ_(transient-cooling), ΔT_(capacitor) decreases close to the ambientduring steady state operation.

In an embodiment of the present disclosure, a pulse width modulated(PWM) controller is used to control electrical energy supplied tothermoelectric devices 102 and reduce the magnitude of Q_(electrical).Consequently, the total amount of heat (Q_(total)) rejected bythermoelectric cooling apparatus 600 is reduced to the amount of heatrejected during the steady state, Q_(total-ss).

Q _(total-ss) =Q _(HP) +Q _(capacitor)  (7)

The total amount of heat transferred by thermoelectric cooling apparatus600 during the steady state (Q_(total-ss)) is less than the total amountof heat rejected by thermoelectric cooling apparatus 600 (Q_(total)).

Thermoelectric devices 102 should always be switched ON to prevent aback flow of heat from second container 604 containing warm fluid 308 tocold fluid 310 present in first container 602. Hence, Q_(electrical)never becomes zero (Q_(electrical)≠0) during the steady state heattransfer.

FIG. 7 illustrates a cross-sectional view of a thermoelectric coolingapparatus 700, in accordance with yet another embodiment of the presentdisclosure.

In addition to the components explained in conjunction withthermoelectric cooling apparatus 600, thermoelectric cooling apparatus700 comprises a thermal diode 702. Thermal diode 702 is positionedbetween the hot side of thermoelectric devices 102 and heat pipes 606.

When thermoelectric devices 102 are switched ON, heat from cold fluid310 is transferred to cold sink 106. Thermoelectric devices 102 transferthe heat from cold sink 106 to the hot side of thermoelectric devices102. Thermal diode 702 conducts heat from the hot side of thermoelectricdevices 102 to hot sink 108 and heat pipes 606. Further, the thermaldiode 702 also prevents the back flow of heat from heat pipes 606 andhot sink 108. In an embodiment of the present disclosure, thermal diode702 is a vapor diode.

In an embodiment of the present disclosure, thermoelectric devices 102are switched OFF after the completion of the transient stage (initialperiod of cooling cold fluid 310 up to a desired temperature). PWMcontroller is configured to switch OFF the thermoelectric device 102when the transient stage is completed. Further, the PWM controller isalso configured to switch ON the thermoelectric device 102 when thecooling phase is in the transient stage.

As stated above, thermal diode 702 prevents the back flow of heat fromheat pipes 606 and hot sink 108. Hence, when the thermal diode 702 isused with the PWM controller, the electrical power consumed bythermoelectric cooling apparatus 700 (Q_(electrical)) is reduced. Thisimplies that when a desired temperature is achieved in cold fluid 310,thermoelectric devices 102 can be switched OFF.

When heat leakage (Q_(leakage)) is equal to zero, electrical energyutilized by thermoelectric cooling apparatus 700 is zero. Thus, afterreaching a steady state temperature, electrical energy utilized bythermoelectric cooling apparatus 700 (Q_(total-ss)) at the steady statewill be approximately equal to zero. This can be illustrated by thefollowing equation: When, Q_(leakage)=0; Q_(electrical)=0

From equation (7),

Since, Q_(total-ss) is nearly equal to zero,

Q _(HP) =−Q _(capacitor).

Hence, when thermoelectric devices 102 are switched OFF, the thermalcapacitor assembly of second container 604 and warm fluid 308) isdischarged faster by heat pipes.

In an embodiment of the present disclosure, second container 604containing warm fluid 308 is replaced with a phase change material. Inanother embodiment, an encapsulated phase change material can be addedto warm fluid 308.

FIG. 8 illustrates a cross-sectional view of a thermoelectric coolingapparatus 800, in accordance with yet another embodiment of the presentdisclosure.

Thermoelectric cooling apparatus 800 comprises top container 304, bottomcontainer 302, a thermoelectric device 802, a metal standoff 804, a heatpipe 803, a first end 806 of heat pipe 803, a diode section 808 of heatpipe 803, condenser fins 114, fan 116, a second end 810 of heat pipe803, a fin array 812 and cold sink 106.

Thermoelectric device 802 is present at the bottom portion of bottomcontainer 302. Thermoelectric device 802 comprises a hot side and a coldside. The cold side of thermoelectric device 802 is attached to coldsink 106 through metal standoff 804. Further, the hot side ofthermoelectric device 802 is attached to first end 806 of heat pipe 803.Diode section 808 is present between first end 806 and second end 810 ofheat pipe 803. Diode section 808 prevents conduction of heat from secondend 810 to first end 806 of heat pipe 803. Condenser fins 114 and finarray 812 are connected to second end 810 of heat pipe 803. Fin array812 is in contact with warm fluid 308 of top container 304 to dissipateheat to warm fluid 308. Further, fan 116 is attached in close proximityto condenser fins 114. Condenser fins 114 and fan 116 dissipate the heatto the ambient.

When thermoelectric device 802 is switched ON, it absorbs heat from coldfluid 310 that is collected by the cold sink 106. Heat from cold sink106 is conducted to thermoelectric device 802 through metal standoff804. Thermoelectric device 802 dissipates the heat to the hot side. Heatpipe 803 present at the hot side of thermoelectric device 802 absorbsthe heat. Heat pipe 803 transfers the heat to condenser fins 114 and finarray 812. A first portion of the heat absorbed by heat pipe 803 isdissipated by condenser fins 114 to the ambient. Fan 116 facilitates thedissipation of heat from condenser fins 114. Further, a second portionof heat absorbed by heat pipe 803 is dissipated to warm fluid 308through fin array 812.

In an embodiment of the present disclosure, warm fluid 308 and coldfluid 310 are water. Thus, in an embodiment of the present disclosure,thermoelectric cooling apparatus 800 is a water cooler.

FIG. 9 illustrates a cross-sectional view of a thermoelectric coolingapparatus 900, in accordance with yet another embodiment of the presentdisclosure.

Thermoelectric cooling apparatus 900 comprises a container 902,thermoelectric devices 102, metal standoffs 104, cold sinks 106, a fluid904, a heat pipe 906, an insulation 908, a lid 910, an insulationsection 912, condenser fins 114 and fan 116.

Container 902 contains fluid 904 to be cooled. Cold sinks 106 are incontact with fluid 904 so that cold sinks 106 can absorb heat from fluid904. As discussed in conjunction with FIG. 1, the cold side ofthermoelectric devices 102 is attached to cold sinks 106. Further, thehot side of thermoelectric devices 102 is attached to heat pipe 906.Heat pipe 906 comprises insulation section 912 between the first end andthe second end of heat pipe 906 to prevent the conduction of heat fromthe second end to the first end of heat pipe 906. Thus, insulationsection 912 prevents a backflow of heat from heat pipe 906. Insulation908 encloses heat pipe 906 and cold sinks 106, and prevents convectiveheat transfer between fluid 904 and heat pipe 906.

When thermoelectric devices 102 are switched ON, they absorb heat at thecold side and reject the heat at the hot side. Heat from fluid 904 istransferred to cold sinks 106. Thermoelectric devices 102 collect heatfrom cold sinks 106 through metal standoffs 104. Thermoelectric devices102 transfer heat to the hot side of thermoelectric devices 102. Heatpipe 906 conducts the heat from the hot side of thermoelectric devices102 to condenser fins 114. Insulation 908 encloses heat pipe 906 andcold sinks 106 to prevent thermal leakage from heat pipe 906 to coldsinks 106. Lid 910 encloses container 902 to prevent heat leakage fromthe ambient to thermoelectric cooling apparatus 900. In an embodiment ofthe present disclosure, lid 910 is made of materials such as plastic.Condenser fins 114 and fan 116 are configured to dissipate heat frompipe 906 to the ambient.

An advantage of thermoelectric cooling apparatus 900 is that an assemblycomprising cold sinks 106, thermoelectric devices 102, metal standoffs104, heat pipe 906, insulation 908, lid 910, condenser fins 114 and fan116 can be easily assembled with any container on which the lid 910 canbe fitted. Further, thermoelectric cooling apparatus 900 can be used asa portable cooling apparatus very effectively.

FIG. 10 illustrates a cross-sectional view of a thermoelectric coolingapparatus 1000, in accordance with yet another embodiment of the presentdisclosure.

Thermoelectric cooling apparatus 1000 comprises a chamber 1002, lid 910,thermoelectric device 102, metal standoff 104, cold sink 106, a backplate 1006, an evaporator plate 1004, heat pipes 1008, condenser fins114, and fan 116.

Chamber 1002 comprises fluid 904. Cold sink 106 is in contact with fluid904. The hot side of thermoelectric device 102 is attached to evaporatorplate 1004. Further, the cold side of thermoelectric device 102 isattached to metal standoff 104. Metal standoff 104 is attached to coldsink 106. In an embodiment of the present disclosure, insulation 908 isconfigured to prevent heat transfer from thermoelectric device 102, heatpipes 1008, and evaporator plate 1004 to fluid 904. Evaporator plate1004 is attached to the first end of heat pipes 1008. A second end ofheat pipes 1008 is attached to condenser fins 114, which are in closeproximity to fan 116. In an embodiment of the present disclosure, heatpipes 1008 provide unidirectional heat flow from thermoelectric device102. Grommets 1010 facilitate the attachment of an assembly ofthermoelectric device 102, metal standoff 104 and cold sink 106 to backplate 1006.

When thermoelectric cooling apparatus 1000 is switched ON,thermoelectric device 102 absorbs heat at the cold side and rejects heatat the hot side. Heat absorbed from fluid 904 is transferred to coldsink 106. Further, heat from cold sink 106 is transferred to the hotside of thermoelectric device 102 through metal standoff 104. Metalstandoff 104 present between cold sink 106 and thermoelectric device 102is configured to reduce heat leakage between the hot side ofthermoelectric device 102 and cold sink 106. Evaporator plate 1004collects heat from the hot side of thermoelectric device 102. Heat fromevaporator plate 1004 is transferred to condenser fins 114 through heatpipes 1008. Fan 116 facilitates dissipation of heat from condenser fins114 to the ambient. In an embodiment, an assembly of evaporator plate1004, metal standoff 104, thermoelectric device 102 and heat pipes 1008are encased with thermal insulation to prevent convective heat transferbetween fluid 904 and the assembly. Further, the electrical wiring tothe thermoelectric modules is also encased in the same insulation.

FIG. 11 illustrates a cross-sectional view of a thermoelectric coolingapparatus 1100, in accordance with yet another embodiment of the presentdisclosure.

Thermoelectric cooling apparatus 1100 comprises the elements mentionedin conjunction with FIG. 10—chamber 1002, thermoelectric devices 102,metal standoffs 104, cold sinks 106, evaporator plates 1004, heat pipes1008, lid 910, condenser fins 114, fan 116, and insulation 1010.Thermoelectric cooling apparatus 1100 provides an apparatus symmetricwith respect to heat pipes 1008.

Cold sinks 106 are in contact with fluid 904. In an embodiment of thepresent disclosure, fluid 904 is water. Evaporator plates 1004 areattached to the first end of heat pipes 1008. Further, a second side ofevaporator plates 1004 is attached to thermoelectric devices 102. Metalstandoffs 104 are present between thermoelectric devices 102 and coldsinks 106. The second end of heat pipes 1008 is attached to condenserfins 114. In an embodiment of the present disclosure, heat pipes 1008are attached to condenser fins 114 using an epoxy solution. In anotherembodiment of the present disclosure, heat pipes 1008 are attachedthrough an interference fit to condenser fins 114. Fan 116 is in closeproximity to condenser fins 114. In an embodiment of the presentdisclosure, insulation 908 is configured to prevent heat transfer fromthermoelectric device 102, heat pipes 1008, and evaporator plate 1004 tofluid 904.

Thermoelectric devices 102 are configured to transfer heat from fluid904 to heat pipes 1008. A convective heat transfer takes place betweenfluid 904 and cold sinks 106 when thermoelectric cooling apparatus 1100is switched ON. Thermoelectric devices 102 absorb heat at the cold sideand reject heat at the hot side. Heat absorbed from fluid 904 istransferred to cold sinks 106 through metal standoffs 104. From thefirst end of heat pipes 1008, heat is transferred to condenser fins 114with the help of a working fluid present in heat pipes 1008. Insulation1010 prevents the backflow of heat from the hot side of thermoelectricdevices 102 and evaporator plates 1004 to fluid 904.

Heat pipes 1008 conduct heat from evaporator plates 1004. Condenser fins114 facilitate the transfer of heat from heat pipes 1008 to the ambient.Further, fan 116 facilitates dissipation of heat from condenser fins 114to the ambient.

FIG. 12 illustrates a cross-sectional view of a thermoelectric coolingapparatus 1200, in accordance with an embodiment of the presentdisclosure.

Thermoelectric cooling apparatus 1200 comprises a container 1202, aninsulation layer 1204, a fluid inlet 1206, a separator 1208, an outlettube 1210, cold sink 106, metal standoff 104, thermoelectric devices102, heat pipes 110, condenser fins 114, and fan 116.

Container 1202 stores a fluid 1212 to be cooled by thermoelectric device102. Cold sink 106 is in thermal contact with fluid 1212. Separator 1208is located between fluid 1212 and cold sink 106. In an embodiment of thepresent disclosure, separator 1208 is configured to facilitate indirecting fluid 1212 entering through fluid inlet 1206 to make a contactwith cold sink 106. In yet another embodiment of the present disclosure,separator 1208 is present along a length of container 1202. Further, themovement of fluid 1212 through cold sink 106 may facilitate removal of amotionless boundary layer (thermal) which may be present at the fins ofcold sink 106. As a result, cold sink 106 may be more efficient inremoving heat from fluid 1212. Cold sink 106 is attached to a first sideof metal standoff 104. A second side of metal standoff 104 is attachedto the cold side of thermoelectric devices 102. The hot side ofthermoelectric devices 102 is attached to the first end of heat pipes116. The second end of heat pipes 116 is attached to condenser fins 114.Fan 116 is thermally coupled to condenser fins 114 to dissipate heat.

When thermoelectric device 102 is switched ON, the thermal transferstarts from fluid 1212 to cold sink 106. Thermoelectric devices 102transfer heat from cold sink 106 to heat pipes 110. Heat from the secondend of heat pipes 110 is dissipated to the ambient through condenserfins 114 and fan 116. A bottom region of container 1202 comprises fluid1212 which is cold. This fluid is dispensed from the container 1202through outlet tube 1210 on demand. A dispenser (not shown in figure)can be placed at the end of outlet tube 1210 to control the flow offluid 1212. Further, when fluid 1212 is stored in container 1202,insulation layer 1204 prevents heat leakage from the ambient.

FIG. 13 illustrates a cross-sectional view of a thermoelectric coolingapparatus 1300, in accordance with an embodiment of the presentdisclosure.

Thermoelectric cooling apparatus 1300 comprises a container 1302, fluid1212 to be cooled, a cold sink 1304, metal standoff 104, thermoelectricdevice 102, a heat pipe-heat sink assembly 1306, and fan 116. In anembodiment of the present disclosure, container 1302 is enclosed by aninsulation material (not shown in figure).

The direction of flow of fluid 1212 into container 1302 is denoted byarrow 1308. Cold sink 1304 is in contact with fluid 1212. One of thesides of cold sink 1304 is attached to the first side of metal standoff104. The second side of metal standoff 104 is attached to the cold sideof thermoelectric devices 102. The hot side of thermoelectric devices102 is attached to heat pipe-heat sink assembly 1306. Fan 116 isthermally coupled to heat pipe-heat sink assembly 1306. For example, inthe present embodiment, thermoelectric devices 102 are positioned at thebottom side of the container 1302 to increase the amount of fluid 1212that contacts cold sink 1304 before being dispensed.

When thermoelectric devices 102 are switched ON, thermoelectric devices102 start to transfer heat from fluid 1212 to heat pipe-heat sinkassembly 1306. Heat from fluid 1212 is conducted by cold sink 1304. Inan embodiment of the present disclosure, the length of cold sink 1304 isconsiderably high compared with cold sinks 106 (refer to FIG. 1 to FIG.11). The increased length of cold sink 1304 results in greater amount offluid 1212 to be in contact with cold sink 1301, thereby creating moreuniform cooling.

Further, heat from cold sink 1304 is transferred to the first side ofmetal standoff 104. Thermoelectric devices 102 transfer heat from thesecond side of metal standoff 104 to heat pipe-heat sink assembly 1306.In an embodiment of the present disclosure, heat pipe-heat sink assembly1306 comprises heat pipes 1312 embedded into the metal base of heatpipe-heat sink assembly 1306. Heat pipes 1312 help with better spreadingof the heat and reduce the thermal spreading resistance. In anotherembodiment of the present disclosure, heat pipes 1312 can extend out ofheat pipe-heat sink assembly 1306 base and can be inserted into the finsof a heat exchanger. In another embodiment of the present disclosure,heat pipe-heat sink assembly 1306 comprises a thermosyphon. Athermosyphon uses a convective fluid such as alcohol to transfer heat.The convective fluid present in the thermosyphon evaporates initially ata region of contact with a hot surface and condenses later on. Thisresults in the transportation of heat within the thermosyphon. In yetanother embodiment of the present disclosure, heat pipe-heat sinkassembly 1306 may be coupled with another convective or conductive heatrejection apparatus. Usage of heat pipe-heat sink assembly 1306increases heat transfer efficiency of thermoelectric cooling apparatus1300. Heat from the heat pipe-heat sink assembly 1306 is dissipated tothe ambient through fan 116. After cooling, fluid 1212 is dispensed fromthe bottom of container 1302 as denoted by an arrow 1310. A suitabledispensing mechanism may be used, attached to the bottom of container1302, to dispense fluid 1212.

FIG. 14 illustrates a cross-sectional view of a thermoelectric coolingapparatus 1400, in accordance with yet another embodiment of the presentdisclosure.

Apparatus of thermoelectric cooling apparatus 1400 comprises most of theparts in common with thermoelectric cooling apparatus 1200 such ascontainer 1202, fluid 1212, insulation layer 1204, separator 1208,outlet tube 1210, cold sink 106, metal standoff 104, thermoelectricdevices 102, and fan 116. However, a combination of parts forming a heatdissipation apparatus (not labeled in FIG. 14) attached to the hot sideof thermoelectric device 102 is different. The heat dissipationapparatus is a collective term for a heat spreader 1402, a pump 1404,fins 1406, fan 116, and a convective fluid (not shown in figure). In anembodiment of the present disclosure, the convective fluid is water.Forced convection occurs in the heat dissipation apparatus when fluidflow is induced by pump 1404. Other types of convective fluids can alsobe used for the transfer of heat from the hot side of thermoelectricdevice 102.

Thermoelectric devices 102 are configured to transfer heat from fluid1212 to heat spreader 1402. During functioning of thermoelectric coolingapparatus 1400, heat from fluid 1212 is transferred to cold sink 106. Inan embodiment of the present disclosure, separator 1208 is configured tofacilitate transfer of heat from fluid 1212 to cold sink 106. Separator1208 may comprise holes to let fluid 1212 to flow through it. Metalstandoff 104 conducts heat from cold sink 106 and transfers tothermoelectric devices 102. Heat from the hot side of thermoelectricdevices 102 is transferred using the heat dissipation apparatus. Forexample, heat spreader 1402 may comprise passages embedded in a platefor transfer of the convective fluid. The convective fluid carries heatfrom heat spreader to fins 1406. The transportation of the convectivefluid in the heat dissipation apparatus may be facilitated by pump 1404.Fan 116 is configured to dissipate heat from fins 1406 to the ambient.In an embodiment of the present disclosure, fan 116 may be a blower fan.Thus, heat from fluid 1212 is removed using thermoelectric coolingapparatus 1400.

Fluid 1212 cooled by the thermoelectric cooling apparatus 1400 is denserthan the warm fluid that is introduced into container 1202. If required,cold fluid 1212 present at the bottom of container 1202 is dispensedfrom the outlet tube 1210. A dispensing mechanism (not shown in figure)may be included at outlet tube 1210 to control flow of fluid 1212.

FIG. 15 illustrates a cross-sectional view of a cooling apparatus 1500,in accordance with an embodiment of the present disclosure.

Cooling apparatus 1500 comprises fluid treatment devices 1502, draintubes 1508, drain tubes 1510 and thermoelectric cooling apparatus 1200.According to the present embodiment, fluid 1212 is purified or treatedbefore it is cooled using thermoelectric cooling apparatus 1200.However, fluid from any physical or chemical treatment apparatus can bechannelized for cooling. For example, the treatment apparatus may bereverse osmosis equipment for water or distillation equipment forwater/other fluids or the like. According to the present embodiment,treatment devices 1502 comprise treatment chambers 1504, a fluid inlet1506, a fluid outlet 1508, drain tubes 1510, and a collector tube 1512.Further, thermoelectric cooling apparatus 1200 may include a ventingdevice such as a bubbler or the like present in container 1202 torelease an air lock or any trapped bubbles. Arrangement of components inthe present embodiment is an example, provided for illustration, andshould not be construed as limitations.

Untreated fluid 1212 to be treated is introduced into one of treatmentchambers 1504 through fluid inlet 1506. Treatment devices 1502 producewaste fluid or effluents which are removed from treatment chambers 1504through drain tubes 1510. Collector tube 1512 is configured to collectwaste fluid from drain tubes 1510. In an embodiment of the presentdisclosure, waste fluid from treatment devices 1502 is channelized tocool the hot side of thermoelectric device 102.

Working of thermoelectric cooling apparatus 1200 is explained in detailin conjunction with FIG. 12. Thermoelectric cooling apparatus 1200 isprovided for cooling fluid 1212 from treatment devices 1502. Fluid 1212cooled by thermoelectric cooling apparatus 1200 is dispensed on demandusing a dispenser 1514 after cooling.

FIG. 16 illustrates graph 1 depicting variation in input current withtime, and graph 2 depicting variation in temperature with time for athermoelectric cooling apparatus, in accordance with an embodiment ofthe present disclosure.

Graph 1 plots a variation of input current with respect to time duringthe process of cooling a fluid using a thermoelectric cooling apparatusin accordance with the present embodiment. In graph 1, time isrepresented on a horizontal axis 1604 and current is represented on avertical axis 1602. Curve 1606 represents variation in the current inputto the thermoelectric cooling apparatus with time. An optimal currentI_(opt), denoted by 1608 is utilized to cool the fluid initially. Theefficiency of the thermoelectric cooling apparatus is maximized when theoptimal current I_(OPT) is passed through it. After a time denoted by avertical dotted line 1616, a minimum amount of current is passed throughthe thermoelectric cooling apparatus. A constant magnitude of steadystate current I_(ss) denoted by dotted line 1610 is passed through thethermoelectric cooling apparatus to maintain the fluid at a desiredtemperature range.

Graph 2 shows the performance of a thermoelectric cooling apparatus inaccordance with an embodiment of the present invention, and plots thevariation in the temperature of the fluid with time during a process ofcooling.

In Graph 2, time is represented on a horizontal axis 1604, andtemperature is represented on a vertical axis 1612. Curve 1614represents variation of temperature of the fluid with respect to time,and this variation has been indicated by T_(C). Temperature of the fluiddecreases below set point temperature (T_(S)) at the time denoted byvertical dotted line 1616. T_(s) is the target temperature that is to bemaintained in the fluid.

Curve 1618 represents variation of temperature of the hot side of thethermoelectric cooling apparatus. Temperature of the hot side of thethermoelectric cooling apparatus reaches a maximum at the time denotedby vertical dotted line 1616, when the thermoelectric cooling apparatusis switched ON.

Current required to cool the fluid initially is at I_(opt) denoted by1608. When the thermoelectric cooling apparatus is switched ON, the heatrejected by the cooling apparatus is initially high which results inincreased temperature of the hot side. As ΔT across the thermoelectricmodules increases, COP decreases resulting in lower heat pumping fromthe fluid. This results in the temperature of the hot side of thethermoelectric cooling apparatus to saturate to a high value as denotedin 1618 for I=I_(opt). For I=I_(opt), the temperature of the fluid isreduced, as denoted by curve 1614. The temperature of the hot side ofthe thermoelectric cooling apparatus is always higher than an ambienttemperature T₀ denoted by a line 1620. Temperature of the hot side ofthe thermoelectric cooling apparatus is above the ambient temperatureT₀.

ΔT (as labeled in the graph 2) denotes a temperature difference betweenthe hot side temperature of the thermoelectric cooling apparatus and theset point temperature T. After the time denoted by vertical dotted line1616, the thermoelectric cooling apparatus is operated at I=I_(ss),which is the minimum current required to maintain temperature differenceΔT between the hot side temperature of the thermoelectric coolingapparatus and the set point temperature T_(s).

FIG. 17 illustrates graph 3 depicting variation in input current withtime, and graph 4 depicting variation in temperature with time for athermoelectric cooling apparatus, in accordance with another embodimentof the present disclosure.

Graph 3 depicts variation of current with respect to time during theprocess of cooling a fluid using a thermoelectric cooling apparatus, inaccordance with the present embodiment. A vertical axis 1702 representscurrent and a horizontal axis 1304 represents time.

Curve 1706 represents variation of current passed through thethermoelectric cooling apparatus with time.

For an initial period of time, the thermoelectric cooling apparatus ispowered with an optimal current I_(opt) which is denoted by 1708. Whentemperature of the fluid reaches a lower limit of temperature (T_(SL)),a steady state current I_(ss) denoted by 1710 is passed through thethermoelectric cooling apparatus to maintain a set temperature of thefluid. The minimal steady state current I_(ss) is maintained throughcurrent or voltage biasing.

Graph 4 shows the performance of the thermoelectric cooling apparatus inaccordance with an embodiment of the present invention, and plots thevariation in the temperature of the fluid with time during a process ofcooling. Graph 4 also depicts variation of temperature of the hot sideof the thermoelectric cooling apparatus with respect to time.

A vertical axis 1712 represents temperature of the hot side of thethermoelectric cooling apparatus, and a horizontal axis 1704 representstime.

A curve 1714 represents variation of temperature of the hot side of thethermoelectric cooling apparatus. Further, a curve 1716 representsvariation of temperature of the fluid to be cooled after switching ONthe thermoelectric cooling apparatus. A dotted line 1718 represents theambient temperature (T₀). A dotted line 1720 represents an upper limit(T_(SU)) of temperature of the fluid. A dotted line 1722 represents alower limit (T_(SL)) of temperature of the fluid. The difference betweenthe ambient temperature (T₀) and lower limit (T_(SL)) of temperature ofthe fluid is defined as (ΔT_(STEC)), represented by arrow 1724.

The thermoelectric cooling apparatus is switched ON and optimal currentI_(opt) is passed until a time denoted by 1726, when the temperature offluid reaches T_(SL). Thereafter, steady state current I_(ss), which isdenoted by curve 1710 is passed through the thermoelectric coolingapparatus to provide minimum amount of cooling that would offset heatleakage from the hot side of the cooling apparatus. Due to small heatleakage through the insulated walls of fluid enclosure, the temperatureof the fluid starts increasing, which is denoted at curve 1728. Afterthe temperature of the thermoelectric cooling apparatus rises to T_(SU),the current being passed through the thermoelectric apparatus is againincreased to I_(opt) so that the temperature of the fluid startsdecreasing again. The temperature of the hot side of the thermoelectriccooling apparatus is close to ambient temperature T₀, denoted by a curve1730. The cycle of variation of the current through the thermoelectriccooling apparatus is continued to maintain the fluid within the desiredtemperature range.

FIG. 18 illustrates graph 5 depicting variation in input current withtime, and graph 6 depicting variation in temperature with time for athermoelectric cooling apparatus in accordance with yet anotherembodiment of the present disclosure. This is in contrast to FIG. 16 andFIG. 17, where the cooling apparatus was operated at a constant currentI_(opt) during the ON phase.

Graph 5 depicts variation of input current with respect to time duringthe process of cooling a fluid using a thermoelectric cooling apparatus,in accordance with the present embodiment. In graph 5, current isrepresented on a vertical axis 1802 and time is represented on ahorizontal axis 1804. A curve 1806 depicts variation of current for aninitial period of time (represented as a point 1808), when thethermoelectric cooling apparatus is kept switched ON. According to curve1806, the magnitude of current reduces gradually till point 1808.Further, during this period, the magnitude of current given by theequation below is passed through the thermoelectric cooling apparatus:

I(t)=γ(T _(w) −T _(S))  (8)

The magnitude of current is proportional to the temperature differencebetween the temperature of the fluid at any given time (T_(w)) and theset temperature (T_(s)). γ is the constant of proportionality. The valueof current at point 1808 is nearly equal to zero. Due to heat leakagefrom the ambient, the temperature of the fluid starts rising. A dottedline 1812 represents a point on axis 1804 when the temperature of thefluid becomes T_(SU) and the thermoelectric cooling apparatus isswitched ON. At line 1812, there is an abrupt increase in theconsumption of current. A curve 1814 depicts the variation of currentwhen the thermoelectric cooling apparatus is switched ON again. A curve1816 depicts a stage where consumption of current becomes nearly zeroand when the thermoelectric cooling apparatus gets switched OFF.

Graph 6 shows the performance of a thermoelectric cooling device inaccordance with an embodiment of the present invention, and plots thevariation in the temperature of the fluid with time during a process ofcooling.

Graph 6 depicts a variation of temperature of a hot side and a cold sideof the thermoelectric cooling apparatus with respect to time. In graph6, temperature is represented by a vertical axis 1818 and time isrepresented by horizontal axis 1804. Variation of temperature of hotside of the thermoelectric cooling apparatus is represented by a curve1820 and variation of temperature of the cold side of the thermoelectriccooling apparatus is represented by a curve 1826. According to curve1820, the temperature of the hot side of the thermoelectric coolingapparatus initially increases and as the current decreases, the hot sidetemperature decreases to a value near the ambient temperature (T₀),which is represented by a line 1824. When the thermoelectric coolingapparatus is switched OFF, the temperature of the hot side of thethermoelectric cooling apparatus is equal to the temperature of theambient (T₀).

A curve 1826 represents variation of temperature of a cold side of thethermoelectric cooling apparatus. According to curve 1826, thetemperature of the cold side of the thermoelectric cooling apparatusreduces initially up to the time corresponding to line 1808 when thethermoelectric cooling apparatus is switched ON. At time represented byline 1808, the temperature of the fluid reaches T_(SL) and thethermoelectric cooling apparatus is switched OFF. As shown in curve1828, the temperature of the cold side increases from a lowertemperature of the cold side (T_(SL)), represented by a line 1830 to ahigher temperature of the cold side (T_(SU)). When the thermoelectriccooling apparatus is kept switched OFF, temperature of the fluid rises,as shown at curve 1828. As the temperature reaches T_(SU), thethermoelectric cooling apparatus is switched ON at a time represented byline 1812. The temperature of the cold side of the thermoelectriccooling apparatus starts decreasing again as shown by curve 1834. Thetemperature is allowed to decrease to a level T_(SL), represented byline 1830. At time represented by line 1836, the thermoelectric coolingapparatus is switched OFF again resulting in increase of temperature ofthe fluid, represented by a curve 1838. The cycle of variation of thecurrent through the thermoelectric cooling apparatus is continued tomaintain the fluid within the desired temperature range.

FIG. 19 illustrates a flow chart 1900 representing a method of operationof a thermoelectric cooling apparatus.

The method starts at step 1902. At step 1904, the type of current thatis provided for the thermoelectric cooling apparatus is checked. If thecurrent supplied is of Alternating Current (AC) type, it is converted toDirect Current (DC). A user-selected mode is verified at step 1908. Ifthe mode is high power mode, then high power mode parameters areimplemented at step 1910. Subsequently, at step 1918, voltage suppliedto the thermoelectric cooling apparatus is set at maximum voltage(V_(max)). If the selected mode is not the high power mode, thenefficiency mode parameters are implemented at step 1912. The efficiencymode parameters relate to the efficient current biasing of thethermoelectric module. At step 1914, after a predetermined amount oftime, the temperature of fluid (T_(w)) is verified to be within adesired range. If yes, then the voltage is set to minimum voltage(V_(min)) at step 1916. For example, the minimum voltage implemented inthe thermoelectric cooling apparatus, according to the presentembodiment may be sufficient to maintain water in the desiredtemperature range. If not, at step 1918, the voltage is set to maximumvoltage (V_(max)). Subsequently, the fluid is cooled in the desired modeat step 1920. The method stops at step 1922. The above mentioned controlflowchart may be integrated in a printed circuit board with IntegratedCircuits (ICs) for temperature sensing and power switches or any othermeans as suitable.

While the preferred embodiments of the invention have been illustratedand described, it will be clear that the invention is not limited tothese embodiments only. Numerous modifications, changes, variations,substitutions, and equivalents will be apparent to those skilled in theart without departing from the spirit and scope of the invention.

What is claimed is:
 1. A thermoelectric cooling apparatus comprising: one or more thermoelectric devices comprising a hot side and a cold side, wherein the one or more thermoelectric devices are configured to cool a fluid; one or more metal standoffs comprising a first side and a second side, the first side of the one or more metal standoffs being attached to the cold side of the one or more thermoelectric devices, wherein the one or more metal standoffs are configured to transfer heat to the cold side of the one or more thermoelectric devices; a cold sink attached to the second side of the one or more metal standoffs, the cold sink being configured to transfer heat from the fluid to the one or more metal standoffs; one or more heat pipes comprising a first end and a second end, the first end being attached to the hot side of the one or more thermoelectric devices, wherein the one or more heat pipes are configured to assist in transfer of heat from the hot side of the one or more thermoelectric devices to an ambient; and condenser fins attached to the second end of the one or more heat pipes, the condenser fins configured to assist in dissipating heat from the second end of the one or more heat pipes to the ambient.
 2. The thermoelectric cooling apparatus in accordance with claim 1, the thermoelectric cooling apparatus further comprises a hot sink attached to the first end of the one or more heat pipes, wherein the hot sink is configured to assist in dissipating heat from the first end of the one or more heat pipes.
 3. The thermoelectric cooling apparatus in accordance with claim 2, the thermoelectric cooling apparatus further comprises a plurality of screws, wherein the plurality of screws is configured to facilitate attachment of the hot sink and the cold sink.
 4. The thermoelectric cooling apparatus in accordance with claim 2, the thermoelectric cooling apparatus further comprising a plurality of grommets, wherein the plurality of grommets is configured to prevent heat conduction from the hot sink to the cold sink.
 5. The thermoelectric cooling apparatus in accordance with claim 2, the thermoelectric cooling apparatus further comprising a hot sink fan thermally coupled to the hot sink, wherein the fan is configured to dissipate heat from the hot sink to the ambient.
 6. The thermoelectric cooling apparatus in accordance with claim 1, the thermoelectric cooling apparatus further comprising a fan thermally coupled to the condenser fins, wherein the fan is configured to dissipate heat from the condenser fins to the ambient.
 7. The thermoelectric cooling apparatus in accordance with claim 1, the thermoelectric cooling apparatus further comprising an evaporator plate thermally coupled to the hot side of the one or more thermoelectric devices, wherein the evaporator plate is configured to collect heat from the hot side of the one or more thermoelectric devices.
 8. The thermoelectric cooling apparatus in accordance with claim 1, wherein the cold sink comprises at least one of anodized aluminum, copper and nickel.
 9. The thermoelectric cooling apparatus in accordance with claim 1, the thermoelectric cooling apparatus further comprising an insulation material, wherein the insulation material is configured to fill gaps between elements of the thermoelectric cooling apparatus.
 10. The thermoelectric cooling apparatus in accordance with claim 1, the thermoelectric cooling apparatus further comprising a thermal diode positioned between the hot side of the one or more thermoelectric devices and the one or more heat pipes, wherein the thermal diode is configured for unidirectional heat transfer.
 11. The thermoelectric cooling apparatus in accordance with claim 1, the thermoelectric cooling apparatus further comprising one or more containers containing the fluid, wherein one of the one or more containers is configured to function as a thermal capacitor.
 12. A thermoelectric cooling apparatus comprising: one or more thermoelectric devices comprising a hot side and a cold side, wherein the one or more thermoelectric devices is configured to cool a fluid; a cold sink attached to the cold side of the one or more thermoelectric devices, the cold sink being configured to transfer heat from the fluid to the one or more thermoelectric devices; one or more diodic heat pipes comprising a first end and a second end, the first end of one or more diodic heat pipes being attached to the hot side of the one or more thermoelectric devices, wherein the one or more diodic heat pipes are configured to facilitate transfer heat from the hot side of the one or more thermoelectric devices to an ambient; and a fin array attached to the second end of the one or more heat pipes, wherein the fin array is configured to transfer heat from the second end of the one or more heat pipes.
 13. The thermoelectric cooling apparatus in accordance with claim 12, the thermoelectric cooling apparatus further comprising condenser fins attached to the one or more heat pipes, wherein the condenser fins are configured to assist in dissipation of heat from the one or more heat pipes.
 14. The thermoelectric cooling apparatus in accordance with claim 13, the thermoelectric cooling apparatus further comprising a fan thermally coupled to the condenser fins, wherein the fan is configured to dissipate heat from the condenser fins to the ambient.
 15. A thermoelectric cooling apparatus comprising: one or more thermoelectric devices comprising a hot side and a cold side, wherein the one or more thermoelectric devices is configured to cool a fluid; one or more metal standoffs comprising a first side and a second side, the first side of the one or more metal standoffs being attached to the cold side of the one or more thermoelectric devices, wherein the one or more metal standoffs are configured to transfer heat to the cold side of the one or more thermoelectric devices; one or more cold sinks attached to the second side of the one or more metal standoffs, the cold sink being configured to transfer heat from the fluid to the one or more metal standoffs; and one or more heat pipes comprising a first end and a second end, the first end of the one or more heat pipes being attached to the hot side of the one or more thermoelectric devices, wherein the one or more heat pipes are configured to assist in dissipating heat from the hot side of the one or more thermoelectric devices to the ambient.
 16. The thermoelectric cooling apparatus in accordance with claim 15, the thermoelectric cooling apparatus further comprising condenser fins and a fan, the condenser fins being in close proximity to the second end of the one or more heat pipes, wherein the condenser fins and the fan are configured to dissipate heat from the one or more heat pipes to the ambient.
 17. The thermoelectric cooling apparatus in accordance with claim 15, wherein the one or more heat pipes further comprise an insulated section to prevent the conduction of heat from the second end to the first end of the one or more heat pipes.
 18. The thermoelectric cooling apparatus in accordance with claim 15, the thermoelectric cooling apparatus further comprising an evaporator plate thermally coupled to the hot side of the one or more thermoelectric devices, wherein the evaporator plate is configured to collect heat from the hot side of the one or more thermoelectric devices.
 19. A thermoelectric cooling apparatus comprising: one or more thermoelectric devices comprising a hot side and a cold side, wherein the one or more thermoelectric devices are configured to cool a fluid; one or more metal standoffs comprising a first side and a second side, the first side of the one or more metal standoffs being attached to the cold side of the one or more thermoelectric devices, wherein the one or more metal standoffs are configured to transfer heat to the cold side of the one or more thermoelectric devices; a cold sink attached to the second side of the one or more metal standoffs, the cold sink being configured to transfer heat from the fluid to the one or more metal standoffs; and a separator configured to direct the fluid towards the cold sink.
 20. The thermoelectric cooling apparatus in accordance with claim 19, the thermoelectric cooling apparatus further comprising a convective heat dissipation apparatus thermally coupled to the hot side of the one or more thermoelectric devices, the convective heat dissipation apparatus being configured to remove heat from the hot side of the one or more thermoelectric devices to the ambient, wherein the convective heat dissipation apparatus comprises a convective fluid for heat transportation, a heat spreader, a pump, fins and a fan.
 21. The thermoelectric cooling apparatus in accordance with claim 19, wherein the separator comprises a plurality of pores.
 22. A thermoelectric cooling apparatus comprising: one or more thermoelectric devices comprising a hot side and a cold side, wherein the one or more thermoelectric devices are configured to cool a fluid; one or more metal standoffs comprising a first side and a second side, the first side of the one or more metal standoffs being attached to the cold side of the one or more thermoelectric devices, wherein the one or more metal standoffs are configured to transfer heat to the cold side of the one or more thermoelectric devices; a cold sink attached to the second side of the one or more metal standoffs, the cold sink being configured to transfer heat from the fluid to the one or more metal standoffs; and a heat pipe-heat sink assembly attached to the hot side of the one or more thermoelectric devices, wherein the heat pipe-heat sink assembly is configured to dissipate heat from the hot side of the one or more thermoelectric devices to the ambient.
 23. The thermoelectric cooling apparatus in accordance with claim 22, the thermoelectric cooling apparatus further comprising a fan thermally coupled to the heat pipe-heat sink assembly, wherein the fan is configured to dissipate heat from the heat pipe-heat sink assembly to the ambient.
 24. A method of cooling a fluid by using a thermoelectric apparatus, comprising: operating the thermoelectric apparatus at optimum conditions when the temperature of the fluid is not within a predetermined temperature range; determining the temperature of the fluid at predetermined time intervals; and operating the thermoelectric apparatus at steady state conditions when the temperature of the fluid is within the predetermined temperature range.
 25. The method according to claim 24, wherein operating the thermoelectric cooling apparatus at optimum conditions includes supplying an optimum current (I_(opt)) to the thermoelectric cooling apparatus.
 26. The method according to claim 24, wherein operating the thermoelectric apparatus at steady state conditions includes supplying a steady state current (I_(ss)) to the thermoelectric apparatus.
 27. A method of operating a thermoelectric cooling apparatus for cooling a fluid, the method comprising: selecting at least one mode of operation from a plurality of modes of operation for the thermoelectric cooling apparatus; and supplying maximum voltage (V_(max)) or minimum voltage (V_(min)) to the thermoelectric cooling apparatus based on the selected mode of operation.
 28. The method in accordance with claim 27, wherein the plurality of modes includes a high power mode and a power efficiency mode.
 29. The method in accordance with claim 28, the method further comprising switching from V_(min) to V_(max) when the temperature of the fluid is greater than a predetermined temperature (T_(w)). 